The human foot is a highly and complex dynamic structure. It is a biomechanically efficient structure capable of numerous intricate articulations which enable it not only to bear weight but to absorb, channel, and return the energy that makes locomotion possible. These articulations, collectively referred to as pronation and supination, produce a tremendous amount of motion within the foot. In addition, when there is a biomechanical or structural abnormality within the foot, excessive motion and/or orthopedic structural deformities such as bunions, hammertoes, and exostoses can result. Shoes are a relatively recent invention designed to protect and support the foot. Unfortunately, most shoes are not designed to accommodate either the physical structure or dynamic motion of the human foot as it progresses repeatedly through the gait cycle. Many shoes are made of rigid leather or unyielding synthetic materials that create pressure and friction against the foot. When this happens numerous pathological lesions can result. For example, when a person has an orthopedic deformity such as a bunion, hammertoe, or exostosis, discrete pressure points can develop between the underlying osseous structure and the unyielding shoe gear. This results in pain and inflammation of the soft tissue interposed between these two rigid structures. In extreme cases, ulcerations can occur. In milder conditions, this pressure and irritation can result in bursa formation or more frequently in thick, hard, and dessicated stratum cornium commonly known as corns or calluses. As these hard, dry keratotic lesions build up, they create even more pressure, irritation, and pain for the afflicted shoe wearer. In other cases, it is friction between the soft tissue and relatively rigid shoe gear that results in irritation, blister formation, and in extreme cases, skin ulceration and infection.
The art of padding and medicating foot lesions is old and crowded. Over the past 100 or so years there have been numerous unsuccessful attempts to address the need to protect the human foot from the ravages of shoe gear. Likewise, there have been numerous attempts to provide a drug delivery system for the human foot that would allow therapeutic agents to be delivered to the foot without the medication being immediately absorbed or rubbed off the skin by socks or shoes. As described in U.S. Pat. No. 4,842,931, the present invention embodies a device which is simultaneously able to pad an orthopedic deformity, dissipate pressure and friction in a superior manner, and provide a dose of a softening and lubricating agent such as mineral oil, or even a pharmacologically active drug, to the cutis of the afflicted shoe wearer by utilizing an oleaginous viscoelastic gel. The present invention teaches a means for preventing the oil fraction of the gel from bleeding out of the bandage which may result in staining of the sock, shoe, or other article of clothing.
Historically most foot protecting devices have been made of compressible materials such as felt, foam rubber, and the like. For example, Duckworth in U.S. Pat. No. 707,089 teaches a corn shield with an interior cavity designed to relieve pressure and irritation. Lepper in U.S. Pat. No. 832,550 teaches an insole with built-in corn pads and mentions the use of medicated pads. Schultz in U.S. Pat. No. 893,876 describes a foot protector made of multiple layers of material, such as felt, which can be customized by removing one or more of the layers. U.S. Pat. Nos. 2,646,795 & 2,827,049 and Canadian Patents 570,208, 556,497, & 581,808 to Scholl, teach various foot protective pads made of foamed latex or felt and contoured to accommodate a pedal deformity. All of these inventions are made of compressible materials and thus are subject to several intrinsic limitations. When compressible materials, such as felt or foam rubber, are subjected to pressure, air is forced out of the interstices of the material and the volume of the padding material decreases. Concomitantly, the density of the padding material increases. For example, a foam rubber corn pad worn on a digit inside a tightly fitting shoe can be compressed to the point where its density approaches that of a piece of solid rubber. In this condition, the pad of compressible material, functions poorly as a dissipator of pressure and especially horizontal shearing (frictional) forces. By contouring the padding material, which requires multiple manufacturing procedures, devices with limited pressure dissipating but practically no friction dissipating properties can be produced. This problem of friction was addressed by Thompson in U.S. Pat. No. 2,943,623. Thompson teaches a skin plaster made of thin strips of tetrafluroethylene which has an extremely low coefficient of friction. Unfortunately, Thompson's skin plaster lacked the ability to pad or medicate foot lesions. Several inventions have been described which will provide medication to the foot but they all suffer from one or more objections. George's in U.S. Pat. No. 281,487 describes a corn or bunion shield made of layers of leather or chamois with a central aperture and mentions the incorporation of oiled silk to soften and lubricate a corn or callus. Rightmire in Reissue U.S. Pat. No. 13,608 teaches a device consisting of small medication containing cups that are secured to the digit by an elastic strap-like member. These cups can be filled with medication. Prisk in U.S. Pat. No. 2,561,071 describes a holder for subcutaneous administration of medicaments. All of these inventions require that medication be deposited in a receptical and the receptical (the dressing) then be affixed to the wearer. In contrast, the present invention teaches a device where the medication (i.e., Mineral Oil USP) or a pharmacologically active agent is actually a constituent of the viscoelastic gel pad.
Viscoelastic gels have been used in medicine as decubitus ulcer dressings, physical therapy devices such as hand exercisers, and prosthetics such as artificial breast implants King in U.S. Pat. No. 3,419,006 teaches a hydrogel made from polyethelyene oxide which is 96% water. This material is marketed as a blister dressing under the name Second Skin.RTM. (Spenco Medical Corporation, Waco, Tex.). Unfortunately, Second Skin.RTM. is impractical to use as a blister dressing because it is very difficult to attach to the skin it will migrate in response to shoe pressure, and it will dry out when exposed to the air. Spence in U.S. Pat. No. 3,548,420 teaches cushion structures made from an organosiloxane gel. Spence's gel lacks an intrinsic medicinal liquid fraction such as Mineral Oil USP, and furthermore, lacks the elasticity to internally absorb horizontal shearing (frictional forces) when applied in very thin layers, an important consideration for a device worn inside a shoe. Spence in U.S. Pat. No. 4,756,949 teaches a method for producing pad structures made from a PVC resin and a dialkylphthalate plasticizer. Again, these pads impart no medicinal substances to the wearer. Shaw in U.S. Pat. No. 4,380,569 teaches a light weight gel structure which incorporates glass microspheres. Sieverding teaches a hydrophlyic elastomeric pressure sensitive adhesive in U.S. Pat. No. 4,699,146.